<!DOCTYPE html>
<head>
    <meta charset="UTF-8">
    <title>基本盒子</title>
    <style type="text/css">
        body{
            padding:0px;
            margin:0px;
        }
        div{
            width:300px;
            height:300px;
            border:10px solid;
            padding:20px;
            margin:30px;
        }
    </style>
</head>
<body>
    <div>
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    </div>
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</body>
</html>